Known hydraulically-actuated fuel injector systems and/or components are shown, for example, in U.S. Pat. No. 5,168,855 issued to Stone on Dec. 8, 1992, U.S. Pat. No. 5,176,115 issued to Campion on Jan. 5, 1993, and U.S. Pat. No. 5,033,435 issued to Ostarello et al. on Jul. 23, 1991.
In such fuel injector systems, the cyclic operation of the injector and the intermittent communication of high pressure actuation fluid to each injector can i) undesirably add to the structural stresses imposed on various engine components, ii) cause the initial rate-of-injection pressure to be steeper than desired resulting in excessive engine noise and emissions, and/or iii) reducing mean injection pressure.
For example, the fuel injector system disclosed in FIG. 2 of Stone or Campion shows a relatively high pressure actuating fluid inlet manifold comprising a common rail passage and a plurality of rail branch passages. Each rail branch passage intersects a respective annular cavity associated with a respective injector. The annular cavity communicates with an actuating fluid inlet passage of the injector which is selectively opened and blocked by an electronically-controlled valve. When the valve is opened to admit high pressure actuating fluid into the injector, intense pressure waves may propagate between the manifold and the respective injector. These pressure waves may generate unacceptable stresses in the cylinder head generally at the intersection of the rail branch passage and the annulus which may cause component failure. Similarly, when the valve closes to block further communication of actuating fluid into the injector, intense pressure waves may propagate between the manifold and the respective injector which again may induce excessive stresses at the rail branch passage/annulus intersection.
The hydraulically-actuated injectors disclosed in Stone and Campion have a certain amount of inherent control over the initial rate of injection pressure. However, such control may not be always adequate for meeting future stringent emissions standards in some engine applications.
Moreover, conventional hydraulically-actuated injectors typically can have a relatively short injection duration at engine idle conditions. This short injection duration may cause excessive engine noise at idle conditions.
Studies have been conducted in the field of intake/exhaust manifold dynamics for compressible fluids such as air. One notable example is entitled Internal Combustion Engine Intake Manifold Aspiration Dynamics, by T. Miyano and M. Hubbard, published on December 1990 in Volume 112 of the Transactions of the American Society of Mechanical Engineers (ASME). In the above study, the length and diameter of the intake manifold pipe and the throttle body upstream pipe length were varied to effect improved volumetric efficiencies of an engine. Air inlet manifold tuning is also disclosed in U.S. Pat. No. 5,085,177 issued to Ma on Feb. 4, 1992. Fuel inlet manifold tuning is disclosed in U.S. Pat. No. 5,076,239 issued to Mina on Dec. 31, 1991 and U.S. Pat. No. 5,086,743 issued to Hickey on Feb. 11, 1992.
However, applicants are not aware of any prior art in the field of hydraulically-actuated injector fuel systems for controlling the flow of relatively high pressure and incompressible hydraulically actuating fluid between an inlet manifold and the injectors.
The present invention is directed to overcoming one or more of the problems as set forth above.